When constructing a shoe sole, especially those for conventional dress shoes, there is usually little cushioning in the forepart and no cushioning in the heel part of the sole. For example, in a conventional sole for men's dress shoe, the sole includes an outsole and a full sole covering the forepart, arch and heel portions of the outsole. For cushioning, sometimes the full insole has a forepart cavity filled with cork. The thickness of the outsole and insole of this conventional dress shoe is normally no thicker than 11 mm and usually 7-9 mm in thickness.
The lasting margin is the break line between the connection of the outsole to the upper. Normally, the insole or innersole board runs along this lasting margin. For a proper fit inside the shoe, normally only a thin sockliner assembly is above the lasting margin.
Although many have tried to improve cushioning in the heel portion of minimal thickness shoe soles, the result has normally been a tradeoff in the look of the shoe. Attempts to add separate cushioning elements to the heel portion of a sole, especially to the sole of a dress shoe, often result in increasing the thickness of the sole to a sole thickness normally associated with an athletic, walking or orthopedic shoe. Thus, the shoe does not have the minimal thickness sole look which consumers expect of dress shoes. For examples of this problem, see U.S. Pat. No. 3,253,355 to Menken, U.S. Pat. No. 1,942,883 to Shaffer and U.S. Pat. No. 302,190 to Butterfield.
Alternatively, the sole may appear to be the same thickness on the outside, but the cushioning elements or a portion of the insole over the cushioning elements often extend well above the lasting margin into the inside of the shoe. When a cushioning element causes the sole to materially project above the lasting margin at the heel portion of the sole, often the comfort of the fit of the shoe is sacrificed. To try and accommodate the fit problem, often the upper is made taller or otherwise expanded. As with the tradeoff of an increased thickness sole, the resulting increased size of an upper can change the look of a dress shoe away from consumer's expectations.
Examples of the increased cushioning causing projections at the top of the heel portion of the sole are found in U.S. Pat. No. 2,502,774 to Alianiello, U.S. Pat. No. 2,135,135 to Gilkerson et al. and U.S. Pat. No. 840,170 to Story. In U.S. Pat. No. 2,502,774 to Alianiello, holes are cut in the heel and forepart portions of the full insole so that the shoes are not more bulky than shoes of standard construction. However, as illustrated in Alianiello's drawings, the shoe sole has an increased thickness at least in the heel portion of the sole, because a sponge rubber cushioning element rests on a shelf of the insole. Also, cork is added between the sponge rubber and the outsole to obtain the total desired cushioning effect. By obtaining the cushioning with the rubber on the shelf of the insole and with the cork, Alianiello may introduce the problem of shoe fit and may possibly require a modified or expanded upper to address this problem.